Manufacturing method of display device

ABSTRACT

A method for manufacturing a display device of the present invention comprises the steps of forming insulating barriers which surround electrode and project upward from the surface of the electrode, and bringing the whole substrate into contact with water after applying the solution including an acceptor in wet process. According to the present invention, an organic conductive layer can be uniformly formed over a substrate in wet process even if the substrate does not have a smooth surface and has distribution in wettability of the surface.

TECHNICAL FIELD

[0001] The present invention relates to a manufacturing method of adisplay device in which a display portion is formed from a lightemitting element using an organic electroluminescent (hereinafterreferred to as EL) material.

BACKGROUND ART

[0002] An display for displaying an image is one of essentialinformation display mediums for modern life. The display for displayingan image is found as usage in several modes, such as starting from aso-called TV monitor, a liquid crystal display that has been rapidlydeveloped recently, and an organic EL display that is expected thefurther development. Specifically, the liquid crystal display and theorganic EL display are characterized by being able to drive in lowervoltage, and are an important research and development issue in view ofenergy saving.

[0003] Above all, the organic EL display attracts most attention as anext generation flat panel display.

[0004] The emission mechanism of the light emitting element using anorganic EL material used in the organic EL display is the mechanism ofusing a photon, in which a molecular exciton is formed withrecombination of an electron injected from a cathode and a hole injectedfrom an anode in the luminescent center of the electroluminescent filmby being provided with a thin film (hereinafter referred to as anelectroluminescent film) including a luminescent body between theelectrodes and applying current to them, and then the photon is ejectedwhen the molecular exciton returns to a ground.

[0005] Usually, the electroluminescent film is formed with a thin filmhaving a film thickness of less than 1 μm. Further, the light emittingelement using the organic EL material is a self-luminous type element inwhich electroluminescent film itself emits light, backlight used for theconventional liquid crystal display is not required. Therefore, it is abig advantage that the light emitting element can be manufacturedextremely thinner and lighter.

[0006] As described above, the emission mechanism of the light emittingelement using the organic EL material is the mechanism of using aphoton, in which a molecular exciton is formed with recombination of anelectron injected from a cathode and a hole injected from an anode inthe luminescent center of the electroluminescent film by being providedwith the electroluminescent between the electrodes and applying thecurrent to them, and the photon is ejected when the molecular excitonreturns to a ground. Therefore, it is one of requirements to efficientlyinject the hole and the electron into the electroluminescent film formanufacturing an efficient light emitting element.

[0007] As a typical operation condition of the light emitting elementusing an organic EL material, current of approximately 100 mA/cm² isapplied to the electroluminescent film with originally higher electricalresistance. In order to realize the current injection having such ahigher density, a hole injection barrier from the anode and an electroninjection barrier from the cathode are to be reduced as far as possible.Namely, a metal with a smaller work function is to be used as thecathode; on the other hand, a metal with larger work function is to beused as the anode. As for the cathode, the work function can bepractically controlled voluntarily by selecting various metal or alloy.On the contrary, the transparency is required for the anode in the lightemitting element using the general organic EL material, the material forthe light emitting element is limited to the transparent conductiveoxide as it now stands. Considering the stability, the transparency andthe resistivity, several oxide conductive films typified by indium-tinoxide (hereinafter referred to as ITO) must be selected for the anode.

[0008] The ITO electrode is the one doped (added) with tin into theindium oxide, and the tin gets into the substitution site of indium. Thetin and the some oxygen defect become the donor, and conductivity isdeveloped by partly filling the conductive band. The ITO is formed overa glass by sputtering, ion beam sputtering, vapor growth method, or thelike. The lower resistance electrode with higher transparency can bemanufactured by choosing the adequate amount of tin doping.

[0009] However, because the surface of the ITO film is not alwaysflattened, it is pointed out that the contact with an electroluminescentfilm used for the light emitting element using the organic EL materialis deteriorated or a pin hole is generated in the electroluminescentfilm. And it is said that is a reason of the deterioration of the lightemitting element using the organic EL material. Further, the workfunction of the ITO film can be varied to some extent according torecord in the film formation or the surface treatment, however thetechnique thereof is limited. Consequently, the reduction of the holeinjection barrier is prevented.

[0010] As a method for reducing the hole injection barrier from ITO filmas the anode, the technique to deposit a buffer layer over the ITO filmis known. To make the adequate ionization potential of the buffer layer,the hole injection barrier can be reduced. The buffer layer is referredto as a hole injection layer. A substance that functions as the holeinjection layer can be roughly categorized by metal oxide, low molecularorganic compound, and high molecular compound. A conjugated polymer suchas polyaniline (refer to non-patent literature 1) and polythiophenederivative (refer to non-patent literature 2) are known as the highmolecular compound material. The conjugated polymer such as thepolyaniline and the polythiophene rarely has conductivity by itself. Andby mixing with strong acid such as camphor sulfonic acid and poly(styrenesulfonic acid) as acceptor, namely by doping, higherconductivity is developed. Accordingly, the conductive conjugatedpolymer which has been doped functions as the hole injection material.

[0011] (Non-Patent Reference. 1)

[0012] Y. Yang et al., Applied physics letters, Vol. 64, 1245 page, 1994

[0013] (Non-Patent Reference. 2)

[0014] S. A. Carter et al., Applied physics letters, Vol. 70, 2067 page,1987

[0015] By using the conductive conjugated polymer which has been dopedas the hole injection layer, the hole injection barrier is reduced andthe hole can be efficiently injected. As a result, the efficiency andthe lifetime of the light emitting element using the organic EL materialcan be improved, and the drive voltage can be reduced. The conductivityconjugated polymer is characterized by being able to be formed over theITO surface in wet application method or ink-jetting.

[0016] A method of obtaining hydrophilic property of the substrate byusing UV ozone rinsing or oxygen plasma rinsing is widely conducted sothat the conductive conjugated polymer is uniformity formed in wetprocess against the substrate surface having the ITO.

DISCLOSURE OF INVENTION

[0017] (Problem to be Solved by the Invention)

[0018] In the case of manufacturing an organic EL display wherein eachpixel is formed from a light emitting element using an plurality oforganic EL material, there is a problem that even an organic conductivelayer is to be formed over a substrate having a pixel electrode (ITO orthe like) corresponding to the each pixel as described above, an uniformlayer is not able to be obtained. The substrate, specifically thesubstrate mounted with a thin film transistor (hereinafter referred toas a TFT) is provided with a barrier having electric isolation so as toisolate each pixel electrode, thus surface smoothness becomes worse, anddistribution in wettability of a substrate surface is occurred.

[0019] The wettability of the substrate is evaluated by measuring acontact angle of a droplet which is dropped to the substrate surface.When liquid is dropped on the solid surface, the droplet is formed onthe solid surface. An angle formed by the liquid surface and the solidsurface is referred to as a contact angle θ(Contact Angle θ). And such aphenomenon of the liquid and solid is referred to as Wetting.

[0020] In the case where there is distribution in the wettability of thesubstrate, soon after a conductive conjugated polymer is applied, theapplied solution coheres to the place having higher wettability when theapplied solution is water-soluble. There is a case where unevennesscaused at this time is not dissolved by spinning; therefore an even thinfilm can not be obtained.

[0021] Accordingly, an object of the present invention is to provide amanufacturing method in which an organic conductive layer comprisingdopant can be formed uniformly to the substrate over which the organicconductive layer can not be uniformly formed.

[0022] (A Means for Solving Problem)

[0023] The present invention comprises a method for manufacturing adisplay device comprising the steps of: forming plurality of firstelectrodes corresponding to plurality of pixels arranged in matrix overan insulating surface of a substrate; forming insulating barriers whichsurround the first electrode and project upward from the surface of thefirst electrode; forming an organic conductive layer comprising anacceptor over the insulating barriers and the first electrode; formingan electroluminescent layer comprising an organic compound which iscapable of emitting electroluminescent light over the organic conductivelayer; and forming a second electrode over the electroluminescent layer,wherein a step of forming the organic conductive layer comprises: afirst step of applying a solution or a dispersion liquid which includesthe same substance as the acceptor in wet process; a second step ofbringing the substrate into contact with water; and a third step ofapplying a solution or a dispersion liquid including a substance forconstituting the organic conductive layer in wet process.

[0024] As described above, by performing the first and the second stepsbefore the step of applying the solution or the dispersion liquidincluding the substance for constituting the organic conductive layer inwet process (the third step as described), the organic conductive layercan be uniformly formed in wet process even if the substrate does nothave a smooth surface and has distribution in wettability of thesurface.

[0025] Further, in terms of wettability in the first step, an organiccompound having sulfonic acid group is preferably used for the acceptor.

[0026] In addition, the concentration of the solution or the dispersionliquid for the acceptor is preferably at least 1 wt % and at most 5 wt %in the first step.

[0027] In a manufacturing method of a display device according to thepresent invention described above, the organic conductive layer isformed in wet application method. Therefore, in the case of using asubstance that a high molecular compound is doped with an acceptor asthe organic conductive layer, the present invention is especiallyeffective.

[0028] The present invention comprises a method for manufacturing adisplay device comprising the steps of: forming plurality of firstelectrodes corresponding to plurality of pixels arranged in matrix overan insulating surface of a substrate; forming insulating barriers whichsurround the first electrode and project upward from the surface of thefirst electrode; forming an organic conductive layer comprising a donorover the insulating barriers and the first electrode; forming anelectroluminescent layer comprising an organic compound which is capableof emitting electroluminescent light over the organic conductive layer;and forming a second electrode over the electroluminescent layer,wherein a step of forming the organic conductive layer comprises; afirst step of applying a solution or a dispersion liquid which includesthe same substance as the donor in wet process; and a second step ofapplying a solution or a dispersion liquid including a substance forconstituting the organic conductive layer in wet process.

[0029] As described above, by performing the first step before the stepof applying the solution or the dispersion liquid of the substance forconstituting the organic conductive layer in wet process (the secondstep as described), the organic conductive layer can be uniformly formedin wet process even if the substrate does not have a smooth surface andhas distribution in wettability of the surface.

[0030] Further, the concentration of the solution or dispersion liquidfor the donor is preferably at least 1 wt % and at most 5 wt % in thefirst step.

[0031] The organic conductive layer is formed in wet application methodin a manufacturing method of a display device according to the presentinvention described above. Therefore, in the case of using a substancethat donor is doped with the high molecular compound, the presentinvention is especially effective.

[0032] The present invention is specifically effective in a method formanufacturing an active matrix type display device.

[0033] Accordingly, in the present invention, the step of forming thefirst electrode further comprises a step of forming a data signal line,a scanning signal line, a nonlinear element connected to the data signalline, the scanning signal line, and the first electrode. At this time,the nonlinear element preferably comprises combination of a thin filmtransistor and a capacitor which are connected each other, orcombination of a thin film transistor and a parasitic capacitor of thethin film transistor.

[0034] (An Effect of the Invention)

[0035] According to a manufacturing method of the present invention, anorganic conductive layer can be uniformly formed by a simple method.Thus, a display device comprising a light emitting element using anorganic EL material can be manufactured with preferable yield and lowercost.

BRIEF DESCRIPTION OF DRAWINGS

[0036]FIG. 1 is diagrams showing images of the present invention.

[0037]FIG. 2 is a diagram showing a system used in an embodiment of thepresent invention.

[0038]FIG. 3 is diagrams showing constitutions of a light emittingelement using an organic EL material manufactured according to thepresent invention in Embodiment 1.

[0039]FIG. 4 is a diagram showing a constitution of a display devicemanufactured according to the present invention in Embodiment 2.

BEST MODE FOR CARRING OUT THE INVENTION EMBODIMENT MODE 1

[0040] A schematic diagram of a method for manufacturing a displaydevice of the present invention is shown in FIGS. 1(A) to 1(F) in theorder corresponding to the steps while showing the cross sections. InFIG. 1(A), the one provided with a first electrode 102 on a substrate101 and an insulating barrier 103 for surrounding the first electrode102 is shown.

[0041]FIG. 1(B) shows a cross sectional view when the solution includingan acceptor is applied over the substrate 101 in wet process as a firststep. A solution layer 104 comprising the acceptor is formed on thefirst electrode 102 and the insulating barrier 103.

[0042] As for the acceptor, an organic compound having sulfonic acidgroup is preferable. For example, poly (styrenesulfonic acid) is givenas an example, and further, aqueous solution is preferable for thesolution including the acceptor.

[0043] Then, a cross sectional view after water is brought into contactover the substrate 101 as a second step is shown in FIG. 1(C).

[0044] As a third step, a cross sectional view when a solution or adispersion liquid including a substance which constitutes the organicconductive layer is applied over the substrate 101 in wet process and anorganic conductive layer 105 is formed, is shown in FIG. 1(D).

[0045] As described, by performing the first and the second steps, theorganic conductive layer 105 can be applied uniformly over the substratehaving uneven wettability in wet process in the third step. That isbecause, for example, in the case that the organic compound havingsulfonic acid group is used as an acceptor, both of hydrophilic grouphaving sulfonic acid group and hydrophobic group having organic groupare included therein, wettability of the insulating barrier surface isthought to be further improved.

[0046] Even more particularly, because of strong electron acceptabilityof an acceptor, the both surfaces of the first electrode 102 and theinsulating barrier 103 are oxidized and the condition of the surfaces asfor the wettability are reformed in a similar condition. The presentinventor considers that this phenomenon is generated not only for theorganic compound having sulfonic acid group but also for the substancehaving electron acceptability. Therefore, in FIG. 1(C), the conditionwhere the layer 104 of the solution including acceptor is remained afterthe second step is illustrated, considering the above reason, the layer104 of the solution including the acceptor is not necessary remained.That is to say, even the solution including an acceptor is entirelywashed away by water during the second step, it is only necessary toreform the surface by the acceptor

[0047]FIG. 1(E) is a cross sectional view when an electroluminescentlayer 106 is formed on the organic conductive layer 105 after the abovedescribed steps. The electroluminescent layer 106 is formed bydeposition or application in a wet process. As the composition of theelectroluminescent layer 106, the structure of the light emittingelement using the known organic EL material is preferably used.

[0048]FIG. 1(F) shows a cross sectional view when a second electrode 107is formed on the electroluminescent layer 106. As the second electrode107, a metal (for example, AlLi alloy, MgAg alloy, or the like) which isto be an electrode is formed by vacuum vapor deposition or EB method andfurther, either the first electrode or the second electrode is to havevisible light transmissivity.

[0049]FIG. 2 shows a schematic diagram of a manufacturing apparatus of alight emitting element using an organic EL material according to themanufacturing method shown in FIG. 1. Hereinafter, an example of formingan electroluminescent layer by vacuum vapor deposition is illustrated.The apparatus is mainly configured of a transfer chamber fortransferring substrates, a delivery chamber for delivery, a depositionchamber for depositing various thin films, and a sealing chamber forsealing. Each chamber is equipped with an exhaust apparatus forachieving necessary vacuum degree or a apparatus for generating a gasatmosphere such as N₂. In addition, the chambers are connected eachother by a gate valve, and the like. The substrates are transferred by atransfer robot.

[0050] A substrate 201 c (it is assumed that a pixel portion, a drivecircuit portion, a wiring, an electrode, a protective film, and the likeare incorporated over the substrate in advance) is introduced into achamber 200 from external. Typically, a TFT is used in the pixel portionand the drive circuit portion. The substrate is set so that the surfacethereof is turned up.

[0051] The chamber 200 into which the substrate 201 c is introducedrepeats exhausting and venting so as to obtain nitrogen atmosphere. Thesubstrate 201 c introduced into the chamber 200 is transferred to atransfer chamber 201 a in normal pressure (nitrogen atmosphere) by atransfer robot 201 b, and then transferred to a UV treatment chamber203. In the UV treatment chamber 203, UV ozone treatment is performedtoward the substrate 201 c. This UV ozone treatment is performed forimproving the wettability of the substrate.

[0052] The substrate that has done the UV ozone treatment is transferredinto a coating chamber 204 through the transfer chamber 201 a. In thecoating chamber 204 in normal pressure (nitrogen atmosphere), an organicconductive layer, specifically, an conductive polymer including theacceptor such as (ethylenedioxy thiophene)/poly (styrenesulfonic acid)aqueous solution (hereinafter referred to as “PEDOT/PSS”) is applied inwet process. There is a case that, the conductive polymer including theacceptor such as PEDOT/PSS can not be uniformly formed over thesubstrate only by UV ozone treatment. For that reason, the solution orthe dispersion liquid including the same substance as the acceptor isapplied in wet process. Specifically, aqueous solution including poly(styrenesulfonic acid) that is an acceptor is spin coated. After spincoating, the substrate is treated with pure water, then PEDOT/PSS isspin coated at the last. After the coating process, the substrate istransferred into an inversion and vacuum bake chamber 202 through thetransfer chamber 201 a. Here, inversion and vacuum bake of the substrateis carried out.

[0053] The substrate 201 c is transferred to a delivery chamber 206after vacuum baking. After delivery chamber 206 is exhausted andevacuated, the substrate 201 c is transferred to a transfer chamber 207kept in a regular vacuum. The transfer chamber 207 is also installedwith a transfer robot which serves to transfer substrates to each of thechambers. Deposition chambers for forming the electroluminescent layerare connected to the transfer chamber 207. In consideration ofmanufacturing a OLED display device of full color display, depositionchambers 208R, 208G and 208B for forming light emitting layers of red,green and blue, and a deposition chamber 209 for forming common layersfor each color, that is, a carrier transporting layer and a carrierinjection layer and the like are installed. In these depositionchambers, vacuum vapor deposition is used in general. In order to obtainfull color emission, a shadow mask for separately applying colors may beused in vapor deposition so as to arrange the light emitting layersshowing emissions of red, green and blue colors respectively in stripes,mosaics or delta shapes.

[0054] The substrate over which film formation of the electroluminescentlayer has done is transferred to a transfer chamber 211 through adelivery chamber 210. A transfer robot is also installed in the transferchamber 211 and serves to transport substrates to each of the chambersconnected to the transfer chamber 211. In a deposition chamber 212 or213, a metal (for example, AlLi alloy, MgAg alloy, or the like) which isto be an electrode is deposited by vacuum vapor deposition or EB method.In an oxygen plasma chamber 214, an organic conductive layer that isadhered to an end face or range margin of the substrate, terminalportion, and a connection region of the cathode and the wiring in thelower part is eliminated. Before performing the oxygen plasma process, ametal to be the electrode by the vacuum vapor deposition or EB methodcan be deposited to the region where the organic conductive -layer is tobe remained. After the oxygen plasma process, the metal to be electrodeis again formed so as to have a contact with the cathode. In adeposition chamber 215, a passivation film (for example, SiN, SiOx film,or the like) for surface protection is deposited generally by sputteringor CVD process.

[0055] The substrate over which film formation has done is transportedto a transfer chamber 217 through a delivery chamber 216. The transferchamber 217 is also connected with a plurality of chambers required forsealing. In the transfer chamber 217, the transfer robot is alsoinstalled, which serves to transport substrates or sealing substrates toeach chamber connected to the transfer chamber 217.

[0056] At first, there is a necessity to prepare a substrate forsealing. For this purpose, a sealing glass substrate preparation chamber218 a and a sealing plastic substrate 218 b are provided.

[0057] In the sealing glass substrate preparation chamber 218 a, acounter glass is introduced from the outside in order to carry outglass-seal to the fabricated OLED. If necessary, a desiccant forpreventing the OLED from moisture can be introduced to the counterglass. For example, a sheet-formed desiccant may be sealed to ashaved-off part previously formed in the counter glass by a double-sidedtape or the like.

[0058] On the other hand, in the sealing plastic substrate preparationchamber 218b, preparation is made for plastic-seal to the fabricatedOLED. The operation may be fully automated, or partially manuallyoperated by setting up gloves.

[0059] The prepared seal glass substrate or seal plastic substrate istransported to a dispenser chamber 219; an adhesive (not shown) forsealing the substrate is applied later. This embodiment mode uses a UVcuring type as the adhesive. If necessary, the desiccant for preventingthe OLED from water (not shown) may be reserved not within the sealglass substrate preparation chamber 218 a during placing a glass butwithin the dispenser chamber 219. For example, a sheet-formed desiccantcan be sealed on a previously formed shaved-off part of a counter glassby a double-sided tape or the like. This eliminates the necessity tohandle the desiccant in the air. The operation may be fully automated,or partly manually operated by setting up gloves. Particularly, in thecase where the seal plastic substrate has curvature and elasticity, theadhesive may be applied to the substrate in a curved state or in astraightly stretched state.

[0060] The substrate completed the deposition, the seal glass substrateor the seal plastic substrate applied with the adhesive are transportedinto a sealing and UV irradiation chamber 220, and then bonded together.During bonding, there is necessity to apply pressure by the use of asuitable jig (not shown). In the case of the seal plastic substratehaving curvature and elasticity, the adhesive may be applied to thesubstrate in a straightly stretched state. The operation may be fullyautomated, or partly manually operated by setting up gloves.

[0061] Then, the substrates that are bonded together in the sealing andUV irradiation chamber 220 are irradiated with UV ray to cure theadhesive.

[0062] The substrate and the seal substrate that are bonded together inthe sealing and UV irradiation chamber 220 may be drawn from a deliverychamber 221 to the outside.

[0063] Next, an example where the electroluminescent layer is formed inwet process is illustrated below. The process until forming the organicconductive layer and baking is carried out as the same method asdescribed above. The substrate that is baked in the inversion and bakechamber 202 is transferred into a coating chamber 205 through thetransfer chamber 201 a while setting the substrate so that the surfacethereof is turn up. In the transfer chamber 205, the long-chain alkylgroup and the like are introduced into the conductive polymerrepresented by poly (phenylenevinylene) and poly (fluorene), therebyforming a film thereover using the soluble derivative solution by spincoating or ink jetting. The material used here is not limited to thehigh molecular compound, and as far as the material can be welldeposited, it can be a low molecular organic compound, or an organicmetal complex. After forming the electroluminescent layer, it istransferred to the inversion and vacuum bake chamber 202 through thetransfer chamber 201 a. Here, inverting and vacuum baking are carriedout.

[0064] The metal formed over the elelctroluminescent layer is preferablyformed as the same way described above. In addition, the substrate usedfor sealing is preferably bonded as the same way described above.

EMBODIMENT MODE 2

[0065] A metal which serves as an electron injection electrode (forexample, AlLi alloy, MgAg alloy, or the like) is formed over thesubstrate by vacuum vapor deposition or EB method. Next, the solutionincluding a donor is applied in wet process. As the donor, alkylammoniumion (for example, tetraethylammonium, tetrabutylammonium, or the like),or Tetrathiafulvalene (hereinafter referred to as “TTF”) are preferable.For the last, the conductive polymer including the donor is applied inwet process. As the conductive polymer, poly (aniline), poly (pyrrole)or the like is preferable.

[0066] The electroluminescent layer can be formed by vapor deposition orapplication in wet process. As the structure of the electroluminenscentlayer, the structure of the light emitting element using the knownorganic EL material is preferably used. As an anode of the holeinjection electrode, an ITO film is preferably used. The ITO film ispreferably formed by sputtering, electron beam deposition, ion plating,or the like.

EMBODIMENT Embodiment 1

[0067]FIG. 3(A) shows a substrate used in this embodiment. And FIG. 3(B)shows a cross sectional view of A-A′ in the drawing. An insulatingbarrier 303 is formed by photolithography over a glass substrate 301 onwhich a transparent electrode 302 of ITO is patterned. The transparentelectrode 302 of the ITO is a rectangle with a film thickness of 100 nmand length of 300 μm and width of 60 μm. The insulating barrier 303 isformed from acrylic resin, which has 1.5 μm height.

[0068] In order to obtain the hydrophilic property of the transparentelectrode 302 of ITO and the insulating barrier 303, UV ozone rinsing iscarried out. Then, 1.5 wt % poly (styrenesulfonic acid) aqueous solutionis spin coated. Pure water is applied to the substrate immediately, andthe substrate is spun to cut the water. Lastly, PEDOT/PSS aqueoussolution is applied over the entire surface so as to obtain the filmthickness of 60 nm by spin coating, prebaked at 80° C. for 10 minutes,baked at 200° C. for one hour, and then vacuum heated just before thedeposition (at 170° C., heating for 30 minutes and cooling for 30minutes). Subsequently, an electroluminescent layer 305 is formed byvacuum vapor deposition without exposing to air.

[0069] Each of an electroluminescent layer 305 and a cathode 306 areformed over an organic conductive layer 304 by vacuum vapor deposition.As the electroluminescent layer,4,4′-bis[N-(3-methylphenyl)-N-phenyl-amino]-biphenyl (hereinafterreferred to as “TPD”) with a thickness of 50 nm, and tris(8-quinolinolate)aluminum (hereinafter referred to as “Alq”) with athickness of 50 nm are deposited. Lastly, AlLi alloy with a thickness of100 nm is deposited as the cathode, thereby manufacturing a lightemitting element using an organic EL material.

[0070] As described above, the organic conductive layer can be depositeduniformly by a simple method according to the manufacturing method ofthe present invention. Therefore, a light emitting element using anorganic EL material can be manufactured with preferable yield and lowercost.

Embodiment 2

[0071] In this embodiment, a light emitting device comprising a pixelportion formed from a light emitting element using an organic ELmaterial by the manufacturing method according to the present inventionis described with reference to a cross sectional view in FIG. 4. A drivecircuit portion and a pixel portion are formed over a substrate 410,here; a source side drive circuit 401 as the drive circuit portion and apixel portion 402 are illustrated.

[0072] A CMOS circuit combined with an n-channel type TFT 423 and ap-channel type TFT 424 is formed in the source side drive circuit 401.Further, a TFT for forming a drive circuit may be formed of a known CMOScircuit, PMOS circuit, or NMOS circuit. In this embodiment, a driverbuilt-in type wherein the drive circuit is formed over the substrate isillustrated, it is not necessary to be the type, and the drive circuitmay be formed not over the substrate but in the exterior of thesubstrate.

[0073] The pixel portion 402 is formed of plural pixels including aswitching TFT 411, a current control TFT 412, and a first electrode 413which is electrically connected to the drain of the current control TFT412. An insulating material 414 is formed so as to cover the edgeportion of the first electrode 413. The insulating material 414 isformed by using a positive type photosensitivity acrylic resin film.

[0074] In order to obtain the preferable coverage, a curved surfacehaving curvature in the top end and the bottom end of the insulatingmaterial 414 is to be formed. For example, in the case of using thepositive type photosensitivity acrylic resin as the material for theinsulating material 414, it is preferable that only the top end of theinsulating material 414 has a curved surface with curvature radius (0.2μm to 3 μm). In addition, either of a negative type which becomesinsoluble to the etchant by the photosensitive light or a positive typewhich becomes solubility to the etchant by the light can be used as theinsulating material 414.

[0075] In order that the first electrode 413 and the insulating material414 have hydrophilic property, UV ozone rinsing is carried out. Afterbeing hydrophilic, PEDOT/PSS aqueous solution is applied to the entiresurface by spin coating. However, there is a case that conductivepolymer including an acceptor such as PEDOT/PSS cannot be uniformlyformed over the substrate only by UV treatment. Therefore, the solutionor the dispersion liquid including the same substance as the acceptor isapplied in wet process. Specifically, aqueous solution including poly(styrenesulfonic acid) which is an acceptor is spin coated. After spincoating, the substrate is spun while covered with pure water. Lastly,PEDOT/PSS is spin coated to form the uniform organic conductive layer.Each of an electroluminescent layer 416 and a second electrode 417 areformed over the organic conductive layer 415, thereby forming anelectroluminescent element 418. Here, a material having larger workfunction is preferably used as a material for the first electrode 413which serves as an anode. For example, in addition to a single layerfilm such as an ITO film, an indium zinc oxide (IZO) film, an titaniumnitride film, a chromium film, a tungsten film, a Zn film, or a Pt film,laminated layer of films of a titanium nitride film and a filmcontaining aluminum as its main component, or a three-laminatedstructure of the titanium nitride film, the film containing aluminum asits main component and titanium nitride film can be used. Further, whenthe laminated structure is used, the resistance as the wiring becomeslower, preferable ohmic contact can be obtained, and it can befunctioned as an anode.

[0076] The electroluminescent layer 416 can be formed by vapordeposition using a vapor deposition mask, or ink jetting. Either of thelow molecular material or the high molecular material can be used forthe electroluminescent layer 416. Further, as the material for theelectroluminescent layer 416, a single layer or laminated layer of theorganic compound is generally used. However, in the present invention,composition using inorganic compound in the one part of the filmcomprising an organic compound may be included.

[0077] Further, a material that has smaller work function (Al, Ag, Li,Ca, or alloy material thereof such as MgAg, MgIn, AlLi, CaF₂, or CaN) ispreferably used as the material used for the second electrode (cathode)417 which is formed over the electroluminescent layer 416. In the casethat light generated in the electroluminescent layer 416 transmits thesecond electrode 417, a laminated layer of a thin metal film with thinfilm thickness, a transparent conductive film (ITO, indium oxide-zincoxide alloy (In₂O₃—ZnO), zinc oxide (ZnO), or the like is preferablyused as the second electrode (cathode) 417.

[0078] As described above, an organic conductive layer can be uniformlyformed with a simple method according to the manufacturing method of thepresent invention; thus, a light emitting element using an organic ELmaterial can be manufactured with a preferable yield and lower cost.

[0079] Industrial Applicability

[0080] As described above, a manufacturing method of the display deviceaccording to the present invention can be applicable for manufacturing adisplay device using an organic conductive layer. Further, theapplication range of the display device obtained by a manufacturingmethod of the display device of the present invention is extremely wide,and the display device can be used in various fields of electricapparatuses.

1. A method for manufacturing a display device comprising the steps of:forming plurality of first electrodes corresponding to plurality ofpixels arranged in matrix over an insulating surface of a substrate;forming insulating barriers which surround the first electrode andproject upward from the surface of the first electrode; forming anorganic conductive layer comprising an acceptor over the insulatingbarriers and the first electrode, forming an electroluminescent layercomprising an organic compound which is capable of emittingelectroluminescent light over the organic conductive layer; and forminga second electrode over the electroluminescent layer, wherein a step offorming the organic conductive layer comprises: a first step of applyinga solution or a dispersion liquid which includes the same substance asthe acceptor in wet process; a second step of bringing the substrateinto contact with water; and a third step of applying a solution or adispersion liquid which includes a substance for constituting theorganic conductive layer in wet process.
 2. A method for manufacturing adisplay device according to claim 1, wherein the acceptor is an organiccompound having a sulfonic acid group.
 3. A method for manufacturing adisplay device according to claim 1 or claim 2, wherein theconcentration of the solution or the dispersion liquid which includesthe same substance as the acceptor is at least 1 wt % and at most 5 wt%.
 4. A method for manufacturing a display device according to claim 1,wherein the organic conductive layer is comprising of a substance thathigh molecular compound is doped with the acceptor.
 5. A method formanufacturing a display device comprising the steps of: formingplurality of first electrodes corresponding to plurality of pixelsarranged in matrix over an insulating surface of a substrate; forminginsulating barriers which surround the first electrode and projectupward from the surface of the first electrode; forming an organicconductive layer comprising a donor over the insulating barriers and thefirst electrode; forming an electroluminescent layer comprising anorganic compound which is capable of emitting electroluminescent lightover the organic conductive layer; and forming a second electrode overthe electroluminescent layer, wherein a step of forming the organicconductive layer comprises: a first step of applying a solution or adispersion liquid which includes the same substance as the donor in wetprocess, and a second step of applying a solution or a dispersion liquidwhich includes a substance for constituting the organic conductive layerin wet process.
 6. A method for manufacturing a display device accordingto claim 5, wherein the concentration of the solution or the dispersionliquid which includes the same substance as the donor is at least 1 wt %and at most 5 wt %.
 7. A method for manufacturing display deviceaccording to claim 5 or claim 6, wherein the organic conductive layer iscomprising a substance that high molecular compound is doped with thedonor.
 8. A method for manufacturing a display device according toclaims 1 and 5, wherein a step of forming the first electrode comprisessteps of forming a data signal line, a scanning signal line, a nonlinearelement connected to the data signal line, the scanning line, and thefirst electrode.
 9. A method for manufacturing display device accordingto claim 8, wherein the nonlinear element comprises a combination of athin film transistor and a capacitor each of which are connectedtogether or a combination of a thin film transistor and a parasiticcapacitor of the thin film transistor.